铕配合物双光子吸收诱导荧光的研究

在合成的一类三元离子缔合型铕配合物Eu(tta)4•DEASP中,阳离子基团DEASP做为铕离子的双光子敏化剂,将铕离子的双光子激发波长拓展至生物光学窗口的长波波段1.06 μm。在此基础上合成出一系列DEASP的衍生物,研究阳离子基团的推拉电子能力对于配合物双光子敏化效率的作用机制。通过改变阳离子基团的端基结构可以有效提高双光子敏化效率,有望获得1.06 μm高效双光子吸收诱导荧光的铕荧光探针。     

[110]晶向近本征硅单晶双光子吸收各向异性

以沿[110]晶向切割的近本征硅单晶为样品,通过研究样品对连续波固体激光器所产生的1.3μm的近红外光的双光子吸收所诱导的光电流对入射光偏振方向的依赖关系,研究了双光子吸收的各向异性.测得了硅单晶对该波长的光的三阶极化率张量χ(3)的各向异性系数为-0.25,两个独立分量的比值χxxxx/χxxyy的幅度为2.4,并基于前期工作所得的χxxyy的结果,进而确定了另一分量χxxxx的值大约为1.49×10-19m2/V2.     

n-InSb的磁双光子带间吸收研究

通过测量光电导和调制光电导,观察到了15K温度下的n-InSb在CW CO_2激光照射产生的磁双光子吸收(TPMA).实验取Voigt位形,磁场沿[111]晶向且最大为4.2T.实验的结果表明,“一次带内,一次带间”跃迁理论可以相当好地解释InSb中的TPMA过程,且大部分吸收为“球对称跃迁”,而其余为较弱的空间反演不对称、斜项和k_H跃迁.通过计算三阶非线性系数虚部得到的TPMA吸收系数与实验测得的双光子光电导之比较亦表明,现有的此方面的理论解释是成立的.     

KBr晶体双光子吸收特性

本文详细研究了ＫＢｒ晶体在室温下经氮分子激光（３３７．１ｎｍ）照射后所产生的双光子吸收的光谱特性及其形成机理。对着色或未着色的晶体仅照射个激光脉冲,就能产生高浓度的Ｆ色心。这是一种在ＫＢｒ晶体中快速产生用于激光和光存储色心的有效途径。     

半导体双光子吸收的阈值光强研究

研究非共振条件下光脉冲在半导体中传输引起的非线性吸收动力学过程，在薄样品近似下推导了描术双光子吸收及其诱导自由载流子吸收相对强弱的阈值光强公式，分析了样品厚度对阈值光强的影响，解释ＧａＡｓ双光子吸收系数的测量值在很大范围内变化的主要原因。     

多光子吸收对差频产生太赫兹波影响的理论研究

理论分析了双光子和三光子吸收对非线性材料差频产生太赫兹(THz)波的影响,在不同抽运功率下,计算了相位失配情况下晶体的最佳作用长度和THz的最大量子转化效率,并将其与相位匹配情况进行对比。研究结果表明,抽运功率不太高时,多光子吸收对差频产生THz波影响不大;随着抽运功率的提高,多光子吸收的影响变得显著;抽运功率较高时,相位匹配与相位失配情况下,双光子和三光子吸收效应都增加了晶体的最佳作用长度,降低了THz的最大转化效率。研究了降低多光子吸收的方法。     

石墨烯量子盘带内跃迁双光子吸收理论研究北大核心CSCD

通过求解无限质量边界条件下石墨烯量子盘(GQDs)电子狄拉克方程,获得了电子能带结构,在此基础上理论研究了石墨烯量子盘的双光子吸收(TPA)性质,得到了任意尺寸分布函数下导带内电子跃迁引起的双光子吸收系数的解析表达式,及双光子跃迁选择定则。研究结果表明,双光子吸收系数的峰值比传统的半导体量子点的大8个数量级左右,石墨烯量子盘的能谱和双光子吸收谱可以通过石墨烯量子点的尺寸、尺寸分布函数和电子的弛豫能来调控。     

应用飞秒激光双光子吸收还原金属离子

为了探讨利用有机高分子材料的飞秒激光双光子吸收来引发金属离子还原的可行性,在自行研制的双光子微细加工系统中,采用物质的量的比为1:1的硝酸银/聚乙烯吡咯烷酮混和凝胶进行还原试验,加工出宽25μm的线条以及4mm×0.4mm的测试导线。由X射线光电子能谱分析可知,加工生成物主要元素是银,通过测试导线电阻,测算其电阻率范围在10-3Ω·m～10-5Ω·m之间。结果表明,用双光子吸收还原金属离子,可以控制反应区域,这对加工导电金属微结构是有帮助的。     

暗孤子传输中的双光子吸收效应的特性研究

用行波法求解了含双光子吸收效应的暗孤子非线性薛定格（NLS）方程,由此孤子解讨论了暗孤子传输特性。     

外加电场双光子光伏光折变晶体中的空间孤子

证明在外加电场的双光子光伏光折变晶体中存在明、暗稳态空间孤子波,它源于双光子光折变效应。结果表明：当光伏效应可以忽略时,这种孤子类似于双光子屏蔽孤子;当没有外加电场时,它退化成闭路条件下的双光子光伏孤子。在不同条件下屏蔽孤子和光伏孤子理论都可以从这一统一理论中得到。     

近红外吸收滤光片的制备与性能研究

将两种近红外吸收剂添加到丙烯酸树脂基体中再与PET薄膜复合,制备了可用于夜视兼容照明的双层复合型近红外吸收滤光片.研究了两种近红外吸收剂的吸收特性,以及近红外吸收剂添加量与滤光片吸收性能的关系,并确定了两种近红外吸收剂的用量.所制备的滤光片在660 ～930 nm波长范围内的光线平均透过率为0.10％,能有效吸收发光器...     

近红外光谱吸收技术的无线电子鼻设计

基于近红外光谱吸收技术,设计并开发出了一套能够高效、准确地对目标气体进行检测的电子鼻系统。电子鼻系统主要包括近红外激光发射单元、气室单元、系统控制单元、人机界面单元。主成分分析(PCA)算法和反向传播(BP)神经网络通过LabVIEW所提供的MATLAB Script节点,集成到上位机软件中,并用来对采集到的数据进行分析。结果表明,该电子鼻在网络训练次数达到1 000次以上时达到稳定,且精度达到0.000 1。对白醋、米醋和苹果醋进行食品分辨,识别准确率达到100%,实现了高精度、高稳定度和高分辨率的设计目标,具有较好的应用前景。     

Optical absorption of vanadium in ZnSe single crystals

The study is concerned with ZnSe:V single crystals produced by diffusion doping. The optical density spectra are recorded in the photon energy range from 0.4 to 3 eV. From the shift of the absorption edge, the vanadium concentration in the crystals is determined. The nature of optical transitions controlling the optical properties of the ZnSe:V single crystals in the visible and infrared spectral regions is identified. The diffusion profile of the vanadium impurity is established from measurements of the relative optical density of the crystals in the visible spectral region. The vanadium diffusion coefficients in ZnSe crystals at temperatures of 1120–1320 K are calculated; at 1320 K, the vanadium diffusion coefficient is 10^?9 cm² s^?1.     

Optical absorption and chromium diffusion in ZnSe single crystals

ZnSe:Cr single crystals were obtained using diffusion-related doping with chromium. The diffusion of chromium was performed in an atmosphere of saturated zinc vapors, and the metallic Cr layer deposited on the crystal surface was used as the source. Lines corresponding to chromium absorption at 2.766, 2.717, and 2.406 eV were observed in the optical-density spectrum at 77 K. The highest chromium concentration in the crystals was determined from infrared absorptance in the region of 0.72 eV and was found to be equal to 8 × 10¹⁹ cm^?3. It is shown that the diffusion profile of the chromium impurity can be determined by measuring the optical density of the crystals in the visible region of the spectrum. The diffusion coefficients D of chromium in ZnSe crystals at temperatures of 1073–1273 K are calculated. An analysis of the temperature dependence D(T) made it possible to determine the coefficients in the Arrhenius equation: D₀ = 4.7 × 10¹⁰ cm²/s and E = 4.45 eV.     

Optical absorption and diffusion of iron in ZnSe single crystals

ZnSe:Fe single crystals obtained by the diffusion doping are studied. The spectra of optical density in the range of energies of 0.4–3 eV are studied. The iron concentration in the studied crystals is determined using the magnitude of the shift of the absorption edge. The nature of the optical transitions determining the optical properties of ZnSe:Fe single crystals in the visible and IR regions of the spectrum is identified. The diffusion profile of Fe impurity is determined by measuring the relative optical density of crystals in the visible spectral region. The diffusivities of Fe in the ZnSe crystals are calculated for temperatures of 1120–1320 K. At 1270 K, the diffusivity of Fe is 3 × 10⁻¹⁰ cm²/s.     

Two-photon absorption for optical clock recovery in OTDM networks

The authors describe the design and performance of an ultrafast optical clock recovery system that is based on two-photon absorption (TPA) in a silicon avalanche photodiode. Unlike many other optical clock recovery techniques, the system is shown to be polarization insensitive, broadband, low jitter, and scalable to high data rates. Moreover, the system is simple, economical, and suitable for integration with silicon electronics. Successful operation of the system is reported for speeds up to 80 Gb/s and transmission distances up to 840 km using a recirculating loop. The authors introduce a new dithering detection scheme that dramatically improves the dynamic range and decreases polarization and wavelength dependence, without introducing an additional timing jitter. The system achieves a dynamic range of 10 dB and optical bandwidth exceeding 35 nm.     

Two-photon absorption coefficients of several liquids at 264 nm

The nonlinear absorption of water (H₂O), heavy water (D ₂O), ethanol, methanol, hexane, cyclohexane, 1, 2-dichloroethane, and chloroform at 264 nm was studied using femtosecond laser pulses. The two-photon absorption coefficients for these liquids were found to be between (34 ± 3) × 10^-11 cm/W and (95 ± 11) × 10^-11 cm/W     

基于近红外吸收光谱技术的高精度CO2检测系统的研制

为了准确测量地震断裂带溢出的痕量CO₂气体浓度,文中采用可调谐半导体激光吸收光谱(TDLAS)技术,选取波数4 978.202 cm-1作为CO₂检测系统的吸收谱线,采用有效光程为40 m的多通池,以STM32作为主控和数据处理核心器件,研制了高精度CO₂检测系统。针对系统中的探测器噪声与光学干涉条纹噪声,利用卡尔曼-小波分析算法滤波提升系统性能。实验表明,与滤波前相比,系统在50 ppmv CO₂浓度下的二次谐波信噪比提升了2.06倍。在不同CO₂浓度下(50、300、1 000、4 000、8 000 ppmv),系统误差为2.57%～2.66%。系统测量4 000 ppmv浓度下的CO2时检测精密度达到20.9 ppmv。利用Allan方差分析得出,积分时间在约61 s时对应的最低探测下限(MDL)为5.2 ppmv,实现了对CO₂气体的高精度测量。结果表明,所设计的高精度CO₂系统可以在气体检测领域为预测地震前兆提供良好前景。     

Excitonic recombination near the mobility edge in CdSe/ZnSe nanostructures

The low-temperature photoluminescence and Raman scattering in CdSe/ZnSe nanostructures with individual CdSe inserts of 1.5 and 3.0 monolayers in nominal thickness were studied. The energy position of the photoluminescene band is governed by interdiffusion of Cd and Zn into the insert regions, whereas the shape of this band is controlled by strong interaction of localized excitons with optical phonons in the Zn_1?xCd_xSe solid-solution insert. Multiphonon processes of excitonic relaxation with involvement of acoustic phonons at the Brillouin zone edges are also important. The results obtained are interpreted in the context of a model for the effective excitonic mobility edge.